Process of producing paramidophenol and its compounds



, 1,501,472 PATENT OFFICE.

mm .1. TEATCHEB, or new YORK, 11. Y.

PROCESS OF PBDDUCING P ABAHIDQPBFENOL AND ITS COIPOUNDB.

Io Drawing.

To all whom it may concern:

Be it known that I, CHARLES J. Tmromm,

a citizen of theUnited States, and a resident of New York city, in the county of- New York and State of New York, have invented certain new and useful Improve- 'ments in the Processes of Producing Paramidophenol and Its Compounds, of which the following ducing is a specification. I The inventlon relates to a process for proparamidophenol base and its salts such as the sulfate (C H,NH OH) H SO,,

: more particularly by the electrolytic reduction of nitrobenzol 1n sulfuric ac1d.- It has for its object to readily and economically produce, on a commercial scale, paramidophenol-base and its salts in a pure condition,

andilparticularly in the case of the salts such as t e sulfate, of a white color. To this end, the process consists of the following steps:

I. Nitrobenzol, preferably redistilled, is

I mixed with or dissolved in sulfuric acid partly diluted to give a content of about 78%. Preferably, brimstone acid free from metals-is used, a good proportion of acid to nitrobenzol being approximately ten .to one; and a convenient quantity for electrolysis in a single. cell is 125 pounds sulfuric acid to 14 ounds'of nitrobenzol. This mixture is designed to be reduced in the cathode compartment of a suitable diaphragm cell of any well-known or special construction, for exam Is a cell such as is set forth in my coendmg application Serial No. 332,228,

led Oct. 21, 1919. A carbon or gother'suit- .able cathode may be employed, and the current density is .maintained at substantially three amperes per square decimeter of electrode surface. The voltage drop thru the cell should not be greater than "about four volts, the amperage being regulated accord.- ingly, and increased with increase of temperature, as the latter is accompanied by a correspondin decrease in the internal re sistanw oft e cell, resulting in decreased electromotive force.

Itwill be found that with a suitable cell, a temperature of 70 to 80 C. is attained, which latter temperature, however, should not be much exceeded. It is desirable to start with a warm or hot mixture ofsulfuric acid, which is conveniently prepared by diluting 1.84 specific ravity' oil of vitriol to the specified strengt just or shortly before starting the electrolysis. The nitrobenzol is best added gradually rather: than by in- Application filed mam '24, 1920. Serial 1n. man.

troducing the full quantity at the start; and it is desirable to keep an excess of mtrobenzolv in the electrolyte which has not been completely reduced. The anolyte should conslst of 50% to sulfuric acid havin anodes consisting preferably of chemical lead sheets; and,--since the anolyte increases in strength as the electrolysis proceeds, the same is to be corrected from time to time by withdrawing a small portion thereof and replacing with the proper quantity of water. To reduce the 14 pounds of nitrobenzol aforesaid, about 6000 ampere hours are re quired, and vigorous and continued stlrrmg is highly desirable.

11. At the conclusion of the electrol sis, after substantiall complete reduction 0 the nitrobenzol, the ot reduced liquor should be immediately withdrawn from the cell and allowed to cool gradually to a temperature of 20 C. or less, which operation may require several days. The cooled liquor crystallizes and has-the appearance of bein solid; but, upon stirring, acquires a semiliquid state, consisting of crystals and ii uor.

II. After having cooled, the liquor is separated from the crude crystals, consisting principally of paramidophenol sulfate, as by filtering same, preferably with suction. This more or less complete separation of the liquor from the crude crystals is desirable in order to obtain a substantially ure product, since neutralization of the hull; of sulfuric acid, together with the crude crystals of paramidophenol sulfate, makes subsequent purification impracticable. The filtration may require a day or more, and should be continued until all the li nor has been removed for the crystals, w 'ch then have a bluish white appearane. At this stage, it is advisable, also, to wash them with more or less concentrated sulfuric acid until substantiall white.

I The crystals. still contain several times their weight of sulfuric acid, which excess of acid must be neutralized. This may be readily accomplished by dissolving the crude crystals in water and addin gradually, with stirring, thin, strainedmil of lime, until the liquid is substantially neut'ral tov Congo red test paper. In order to prevent oxidation or to reduce oxidized compounds, 9. little sulfite, or bisulfite, of soda should be added during the neutralization before its completi0n,or at'least at neoaava times, the washings bein kept separate for washing the next neutra ization, each portion being advanced so that the seventh washing, which starts with pure water, will be the sixth washing on the next neutrali Y zation, and so on.

VII. To prepare the sulfate, the filtrate from the lime sludge, obtained as set forth in step V, and the first washing may now be evaporated, preferably in a vacuum evaporator or an open lead pan, until it crystallizes on cool ng, addin a suitable quantit of sodium sulfite or war t e end of the evaporation and correcting the acidit so that the liquor remains neutral to ongo red test paper.

If the base, or some salt of paramidophenol other than the sulfate, be desired, this is effected by further neutralizin the liquor, obtained as set forth in step preferably with carbonate of lime, which, when cool, gives a mixed precipitate of calcium sulate and of paramidophenol base. The carbonate of lime is added to the more or less dilute solution until there is no more effervescence. The mixed precipitate is then filtered off, and the paramidophenol base can be separated from the calcium sulfate by leechin out with very hot water, the base crysta lizing out again on cooling. The same quantity of water may be used for a second and, if necessary, other extractions. The base so prepared may be filtered off and dried.

Or, if a salt is desired, the base is mixed.

with a suitable quantity, say ten times as much, water, and the acid whose salt :is to be preplared is then added with heating until t e resulting solution is neutral to Congo red test paper. It is then crystallized by cooling or evaporating, as may be necessary. The hydrochloride, for example. may thus be prepared by the addition of hydrochloric acid; or other salts, such'as the acetate, can be thus obtained by adding the corresponding acid.

The liquor resulting from the first crystallization may be evaporated and crystallized time after time until the resulting crystals become impure, at which timethe precipitation of base is carried out just as above described, and the filtrate discarded. It has been my practice to add the final mixed precipitate of calcium sulfate and base to the crude crystals before they are neutralized with lime, as set forth in ste IV.

II. In all cases where pure, white comthermore, be obtained by recrystallizm pounds are desired, the evaporated liquor, obtained as set forth in step VII, should be treated with animal charcoal, while hot, to remove coloring matter.

IX. It should then be cooled to about 3 5 C. and filtered at or about this temperature to remove other impurities.

X. After the filtration is completed, the liquor is further cooled, preferably slowly iand to a substantial degree, until it crystalizes.

XI. The supernatent liquor is then filtered off or drawn off, and the crystals are centrifuged until nearly XILiThe may then be ally dried; or, treated, if esired, .while moist, with ure methyl alcohol to rovide a methy ated paramidophenol sulfate, and then dried, preferably in a vacuumdrier, resulting in a pure, white paramidophenol sulfateor methylated paramidophenol sulfate.

The methylating of the sulfate to produc'e methylated paramidophenol sulfate is effected best by pouring wood alcohol over the. crystals after as much liquor as is p0scrystals are. still moist. The wood alcohol, either by a chemical or physical action, breaks down the crystals more or less, forming a very fine, white powder when dry.

The highest degree of purity may, fulft e paramidophenol sulfate several times rom Water containing animal charcoal and sodium bisulfite.

I claim:

1. In the manufacture of paramidophenol and its compounds, the process of reducing nitrobenzol by electrolyzing. the same. in sulfuric acid, diluted to a content not exceeding about 78%, until the liquor will crystallize when cooled, cooling to crystallize the liquor, filtering off the mother liquor, dissolving the crystals in Water, and neutralizing the excess acid thereof, whereby a paramidophenol compound readily soluble in water is obtained.

2. In the manufacture of paramidophenol and its compounds, the process of reducing nitrobenzol by electrolyzing thesame in sulfuric acid, diluted.to a content not exceeding about 78%, until the liquor will crystal ize when cooled, cooling to crystallize the liquor, filtering oil the mother liquor, dissolving the crystals in water, neutralizingthe excess acid thereof, and introducing a sulfite.

3. The process of manufacturing, electrolytically, paramidophenol sulfate, which consists in electrolyzing nitrobenzol in sulfuric acid, diluted to a content not exceeding about 78%, until the liquor will crystallize when cooled, cooling to crystallize the liquor, filtering off the mother liquor, dissolving the crystals in water and neutralizing 'sible has been centrifuged off and while the the excess acid thereof, introducing a sulfite, evaporating, crystallizing and separating the crystals, and drying the same.

4. The process of manufacturing, electrolytically, paramidophenol sulfate, which consists in reducing nitrobenzolby electrolyzing the same in a cathode compartment with sulfuric acid substantially in the proportion of 14 parts of the former to 125 parts of the latter, which is of a concentration of about 7 8% sulfuric'acid, at a temperature of substantially 75 C. and a current density of substantially three amperes per s uare decimeter of cathode surface, until t e liquor will crystallize when cooled, cooling to crystallize the liquor, filtering off the mother liquor, dissolving the crystals in water, neutralizing the excess. acid thereof, introducing a sulfite, evaporating, crystallizi'ng, separating the crystals, and drying the same.

5. he process of manufacturing, electrolytically, paramidophenol sulfate, which consists in reducing nitrobenzol by electrolyzing the same in a cathode compartment with sulfuric acid substantially in the proportion of 14 parts of the: former to 125 parts of the latter, which is of a concentration of about 78% sulfuric acid, at a tem perature of substantially 75 C. and a current density of substantially three amperes per square decimeter of cathode surface un til the liquor will crystallize when cooled, cooling to crystallize the liquor, filterin off the mother liquor, washing with sul ric acid, dissolving the crystals in water, neutralizin the excess acid thereof, introducing a su fite, evaporating, crystallizing, separatigglthe crystals, and drying the same.

6. e process of manufacturing, electrolytically, paramidophenol sulfate, which consists in reducing nitrobenzol by electrolyzing the same in a cathode compartment with sulfuric acid substantially in the proportion of 14 parts of the former to 125 parts of the latter, which is of a concentration of about 78% sulfuric acid, at a temperature of substantially 75 C. and a current density of substantially three amperes per square decimeter of cathode surface until the liquor will or stallize when cooled, cooling to crystallize t e liquor, filterin off the mother liquor, washing with sul ric acid, dissolving the crystals in water, neutralizing the excess acid thereof with calciuni hydrate, introducing a sulfite, evaporating, crystallizing, separating the crystals, and drying the same.

7. The proce s of manufacturing, electrolytically, para idophenol sulfate, which consists in reducing nitrobenzol by electrolyzing the same in a cathode compartment with sulfuric acid substantially in the proportion of 14 parts of the former to 125 parts of the latter, which is of a concentration of about 78% sulfuric acid, at a temperature of substantially 75 C. and a current density of substantially three amperes per. square decimeter of cathode surface until the liquor will crystallize when cooled, cooling to crystallize the liquor, filtering off the mother liquor and washing the crystals with sulfuric acid, dissolving the crystals in Water, neutralizin the excess sulfuric acid by adding milk 0 lime untilthe liquor is neutral to Congo red test aper and introducing a sulfite, filtering ofi the liquor from the precipitated lime sludge and washing the latter a number of times with water, evaporating the filtrate until it crystallizes when cooled and correcting for acidity, treating with animal charcoal and filtering at about-35 0., cooling the 'liquorto crystallize same, withdrawing the mother liquor, and finally thoroughly drying the crystals.

8. The process of manufacturing, electrolytically, paramidophenol sulfate, which consists in reducing nitrobenzol by electrolyzing same in sulfuric acid until the liquor will crystallize when cooled, cooling to crystallize the liquor, filtering off the mother liquor, dissolving the crystals in water and neutralizing the excess acid thereof with calcium hydrate, introducing a sulfite, filtering, evaporating, chystallizing and separating the crystals, drying the same, and recrystallizin 9. Ihe process of manufacturing, electrolytically, paramidophenol sulfate, which consists in reducing nitrobenzol by, electrolyzing same in sulfuric acid until the liquor will crystallize when cooled, cooling to crystallize the liquor, filtering off the mother liquor, dissolving the crystals in water and. neutralizing the excess acid thereof, introducing a sulfite, filtering, eva oratin ,j crystallizmg and separatin t e crysta s, treating with methyl alcoho, and drying.

10. The process of manufacturing, electrolytically, paramidophenol sulfite, which consists in reducing nitro-benzol byelectrolyzing same in sulfuric acid until the liquor will crystallize when cooled, cooling to crystallize the liquor, filtering off the mother liquor, dissolving the crystals in water and neutralizin the excess acid thereof, introducing a sul te, filtering, evaporatin crystallizmg and separating the crysta s, partly dr ing the cr stals, treating with methyl alcoho andfurt er drying.

11. The herein-described product consisting of paramidophenol sulfate in the form of a dry white powder. 7

12. In the manufacture of paramidophenol and its compounds, the process of reducing nitrobenzol by electrolyzing the same in sulfuric acid until the iquor willcrystallize when cooled, cooling to crystallize the liquor, filtering off the mother liquor, dissolving the crystals in water, neutralizing the excess acid thereof, introducing a sulfite, filtering, further neutralizin with calcium hydrate, filtering off the precipitate and separating the paramidophenol base.

13. In the manufacture of paramidophenol and its compounds, the process of reducing nitrobenzol by electrolyzing the same in sulfuric acid until the liquor will crystallize when cooled, coolin to crystallize the liquor, filtering oil the mot er liquor, dissolving the crystals in water, neutralizing the excess acid thereof, introducing a sulfite, filtering further neutralizing with calcium carbonate,

filtering oil the precipitate and separating the paramidophenol base by leeching out with hot water, cooling to crystallize the base, filtering, and drying.

14. In the manufacture of paramidophenol and its compounds, the process of reducing nitrobenzol by electrolyzing the same in sulfuric acid until the liquor will crystallize when cooled, cooling to crystallize the liquor, filtering off the mother liquor, dissolving the crystals in water, neutralizing the excess acid thereof, introducing a sulfite, filtering further neutralizing with calcium carbonate, filtering off the precipitate and separating the paramidophenol base by leeching with hot water, cooling to crystallize the base, filtering, redissolving by adlding an acid to form a paramidophenol sa t.

15. In the manufacture of paramidophenol and its compounds, the process of reducing nitrobenzol by electrolyzing the same in, sulfuric acid until the liquor will crystallize when cooled, cooling to crystallize the li uor, filtering oil the mother liquor, disso ving the crystals in water, neutralizing the excess acid thereof, introducing a sulfite, filtering, further neutralizing with calcium carbonate, filtering oil the precipitate and separating the paramidophenol base by leeching with hot Water, cooling to crystallize the base, filtering, adding an acid with heating and until the resultlng solution is neutral to Congo red test paper, and then evaporating to crystallization.

Signed at New York, in the county of New York and State of New York, this 23rd day of January A. D. 1920.

CHARLES, J. THATCHER. 

